Chain drive systems are often utilized in many drive systems, such as those found in internal combustion (IC) engines. These chain drive systems include drive chains and sprockets that can transfer rotational power from the crankshaft to such components as camshafts, balance shafts, water pumps, and oil pumps. An example of a chain drive system is disclosed in U.S. Pat. Nos. 7,293,538 and 6,923,154. Inherent to these systems is a meshing noise that occurs between the drive chain and sprockets.
Elastomeric or compression rings applied to chain sprockets are known and are often utilized to dampen or reduce the meshing noise between a drive chain and a chain sprocket. U.S. Pat. No. 6,179,741 describes such a compression ring. In some instances, excessive wear of the compression rings occurs and can reduce the effectiveness of noise abatement over the lifetime of the sprocket component or IC engine.
FIGS. 10 through 12 show a prior art chain and sprocket system 100 that includes a sprocket 110, and a chain assembly 114. The sprocket 110 includes a plurality of teeth 118 arranged circumferentially and projecting radially from a middle portion of a hub 112. A first compression ring 113A is arranged on a front portion of the hub 112, axially adjacent to the teeth 118, and a second compression ring 113B is arranged on a rear portion of the hub 112, axially adjacent to the teeth 118. The first compression ring 113A includes a first compression pad 115A, a second compression pad 115B, and a third compression pad 115C amongst several compression pads arranged circumferentially on the compression ring 113A.
The chain assembly 114 includes a first, second and third link plate 119A-119C, and pins 108A-108C that engage the plurality of teeth 118 arranged around the circumference of the sprocket 110. The height of first and third link plates 119A and 119C are equivalent, denoted as H1 within FIG. 10; the height of the second link plate 119B, denoted as H2 within FIG. 11, is smaller than the height H1 of the first and third link plates 119A, 119C.
Referring to FIG. 11, the three compression pads 115A-115C, shown in an uncompressed state, have an identical surface profile 116 and are aligned with the first 119A, second 119B, and third link plates 119C. Additionally, a radial distance X1, X2, and X3 from an outer-most portion of the profiles 116 of the three compression pads 115A-115C to a central axis 102 is constant; thus, X1=X2=X3. Compression pads are typically made out of an elastomeric material, providing a resistive force when compressed by an interfacing link plate, to counteract a rapid engagement of sprocket teeth 118 by the pins 108A-108C of the chain assembly 114. Due to the smaller height H2 of the second 119B link plate compared to the first 119A and third 119C link plates, and the previously described equi-distant profiles 116 of the three compression pads 115A-115C, the second compression pad 115B will be compressed less than its neighboring first 115A and third 115C compression pads. This unequal compression will result in unequal resistive forces or damping characteristics, potentially resulting in undesirable noise and excessive wear on the first and third compression pads 115A, 115C.
A durable solution is required that provides for effective noise abatement for chain assemblies that have link plates of differing forms and/or sizes.